The present invention relates to a pilot burner, a premixing combustor, and a gas turbine that generate a stable flame.
FIG. 8 depicts a pilot burner and a main burner of a premixing combustor in a conventional gas turbine. A pilot burner 70 consists of an outer cylinder 71, a pilot swirler 72, a pilot nozzle 73 and a pilot cone 74. Fuel is injected and diffused in the premixing combustor, as shown by black arrows 75, from the pilot nozzle 73. A plurality of premixing nozzles 76 those inject premixed gas are provided around the pilot nozzle 73. This fuel injected from the pilot nozzle 73 is burnt in the form of a flame and this flame helps combust the premixed gas injected from the premixing nozzles 76.
Pilot air is made to flow from left (xe2x80x9cupstreamxe2x80x9d) to right (xe2x80x9cdownstreamxe2x80x9d) as shown by white arrows. The pilot swirler 72 functions to circulate the pilot air around the pilot nozzle 73 to improve the combustion efficiency. The pilot swirler 72 surrounds the pilot nozzle 73. However, the pilot swirler 72 is not directly attached to the pilot nozzle 73 but arranged towards the side of the outer cylinder 71.
The combustion of the premixed gas is conducted at a high temperature of about 1500 degree centigrade to suppress generation of toxic thermal NOx gas. However, the combustion of the fuel is conducted at relatively low temperature. As a result, thermal NOx is disadvantageously generated during the combustion of the fuel.
The amount of thermal Nox generated may be reduced by reducing the amount of the fuel. However, if the fuel reduced, the flame obtained by burning the fuel becomes unstable. In the worst case the flame may be extinguished because of the blow of the pilot air. Since this flame has a great influence on the combustion of the premixed gas, it is preferable that the flame is stable and does not extinguish.
It is an object of this invention to provide a stable flame.
According to a pilot burner of one aspect of the present invention, a pilot nozzle diffusion-injects a fuel, a pilot swirler swirls a pilot air around the pilot nozzle, an air guide is arranged between the outer surface of the pilot nozzle and the pilot swirler. The air guide extends from the pilot swirler to a tip of the pilot nozzle. The air guide has a tip that protrudes beyond the tip of the pilot nozzle and this the tip of the air guide is bent away from a center of the pilot nozzle.
According to a pilot burner of one aspect of the present invention, a pilot nozzle diffusion-injects a fuel, a pilot swirler swirls a pilot air around the pilot nozzle, an air guide is arranged between the outer surface of the pilot nozzle and the pilot swirler. The air guide extends from the pilot swirler to a tip of the pilot nozzle. The air guide has a tip that protrudes beyond the tip of the pilot nozzle and this the tip of the air guide is bent radially with respect to a center of the pilot nozzle.
The premixing combustor according another aspect of the present invention is provided with the pilot burner according to the present invention.
The gas turbine according still another aspect of the present invention is provided with the pilot burner according to the present invention.
Other objects and features of this invention will become apparent from the following description with reference to the accompanying drawings.